Ethylene glycol esters as photoactive agents

ABSTRACT

New compounds useful in photodynamic therapy are of the formula and their 1,4-diene isomers and the metallated and/or labeled and/or conjugated forms thereof wherein each R1 is independently alkyl (1-6C); each n is independently an integer of 0-6; and R2 is vinyl or a derivative form thereof.

This application is a continuation of U.S. Ser. No. 09/088,524, filedJun. 1, 1998 and now U.S. Pat. No. 5,929,105, which is acontinuation-in-part of U.S. Ser. No. 08/852,494, filed May 7, 1997 andnow abandoned, the contents of both applications being incorporated byreference herein.

TECHNICAL FIELD

The invention relates to compounds useful in photodynamic therapy (PDT)and related applications. In particular, it concerns ethylene glycolesters of monohydrobenzoporphyrins.

BACKGROUND ART

Photodynamic therapy (PDT) generally involves the administration ofcompounds that are capable of absorbing light, typically in the visiblerange, but also in the near ultraviolet, followed by irradiation oflocations in the subject for which a toxic or inhibitory effect isdesired. PDT was initially developed using hematoporphyrin and relatedcompounds in the treatment of tumors, as it appeared that thesecompounds would "home" to locations containing rapidly dividing cells.The tumor could then be irradiated with light absorbed by thehematoporphyrin and destruction of the surrounding tissue resulted. PDThas since been shown to be useful for treatment of atheroscleroticplaques, restenosis, infections in the blood stream, rheumatoidarthritis, psoriasis and in the treatment of ocular conditions notnecessarily limited to tumors.

U.S. Pat. No. 5,171,749 and patents issuing on related applications,U.S. Pat. Nos. 5,283,255; 5,399,583; 4,883,790; 4,920,143; and5,095,030; all of which are incorporated herein by reference, describeand claim a class of photoactive compounds useful in PDT designated themonohydrobenzoporphyrins, or "BPDs." This class is obtained byDiels-Alder reaction of a mono- or disubstituted alkyne withprotoporphyrin-IX and the resultant compounds can further be isomerized,reduced, and/or derivatized to obtain a large class of BPDs. Asdisclosed in these patents, a particularly useful subclass of this groupresults from hydrolysis or partial hydrolysis of the ester groups of the2-carboxyethyl side-chains on rings C and D. Esterification asprotection of these groups during the Diels-Alder reaction results ininitial products which contain 2-carbalkoxyethyl groups. It was foundthat facile hydrolysis of these esters could readily be conducted,leaving any carbalkoxy groups associated with the Diels-Alder productobtained from a dicarbalkoxyalkyne virtually completely unhydrolyzed.This resulted in four species of compounds, BPD-MA, BPD-MB, BPD-DA andBPD-DB as depicted in FIG. 1; this figure taken from U.S. Pat. No. 105,171,749. In this depiction, R¹ and R² are carbalkoxy groups, typicallycarbomethoxy or carboethoxy, and R is alkyl (1-6C).

BPD-MA was found to have particularly useful properties for PDT and iscurrently in clinical development. However, there remains a need foradditional specific forms of photoactive agents which expand therepertoire of photoactive compounds for the variety of indications towhich PDT is applied, as noted above. The present invention providescompounds in which rings C and D contain ethylene glycol esters of thecarboxyalkyl substituents. These compounds have pharmacokineticproperties which are advantageous in certain instances where PDT isemployed.

DISCLOSURE OF THE INVENTION

The compounds of the invention are useful new additions to therepertoire of compounds that find application in photodynamic therapyand related methodologies that employ photoactive compounds. Thepresence of ethylene glycol esters in these molecules provides them withcharacteristics that permit expansion of the scope of conditions underwhich such photoactive compounds are employed and fine tuning of thetreatment.

Thus, in one aspect, the invention is directed to compounds of theformula ##STR2## and the metallated and/or labeled and or conjugatedforms thereof wherein R¹ is alkyl (1-6C), preferably methyl, n is aninteger of 0-6, preferably 2, and R² is vinyl or a derivative thereof,preferably vinyl.

The invention also is directed to compounds of the formula ##STR3## andthe metallated and/or labeled and or conjugated forms thereof whereinR¹, n, and R² are defined as described above. These analogs are derivedfrom protoporphyrin III and protoporphyrin XIII respectively, in amanner similar to that in which the compounds of formulas 1 and 2 arederived from protoporphyrin IX. The invention also includes isomers ofthe various forms of formulas 1-4 which result from the unrearrangedDiels-Alder condensation products (i.e., the 1,4-diene) as described inU.S. Pat. No. 4,883,790, incorporated herein by reference. Thesestructures are also set forth in FIG. 14.

In other aspects, the invention related to methods of diagnosis andtreatment using the compounds of formula 1, 2, 3 or 4 or their 1.4-dieneisomers, as shown in FIG. 14, or mixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the compounds of the prior art, BPD-MA, BPD-MB, BPD-DA andBPD-DB.

FIG. 2 shows the kinetics of uptake of B-EA6 by L1210 cells.

FIG. 3 shows the kinetics of release of B-EA6 by L1210 cells.

FIG. 4 shows a graphic depiction of the pharmacokinetics of B-EA6 invivo.

FIG. 5 shows a comparison of the kinetics of uptake of B-EA6 by normalsplenocytes and L1210 cells.

FIG. 6 shows the time course of PDT using B-EA6 in mice as compared tomice treated with BPD-MA and BPD-MB.

FIG. 7 shows the effect of B-EA6 on microvasculature in mice.

FIG. 8 shows a comparison of the spectra in plasma of BPD-MA and B-EA6.

FIGS. 9A and 9B show the cytotoxic effect of photodynamic treatmentusing A-EA6 in comparison with BPD-MA in L1210 cells and in dendriticcells.

FIG. 10 shows the comparative effects of A-EA6 and BPD-MA in decreasingthe surface expression of MHC I receptors.

FIG. 11 shows the effect of photodynamic therapy using A-EA6 and BPD-MAon stress and mitogenic pathway kinases in HL60 cells.

FIG. 12 shows the comparative effect of PDT using A-EA6 and BPD-MA oncaspase activation in HL60 cells.

FIG. 13 shows the comparative effect of PDT using A-EA6 and BPD-MA onDNA fragmentation in HL60 cells.

FIG. 14 shows the structures of the unrearranged Diels-Alder productsthat are precursors to the compounds of formulas 1-4.

MODES OF CARRYING OUT THE INVENTION

The compounds of the invention are related to those disclosed in the BPDpatents cited above, but differ in that they contain esters of ethyleneglycol in the substituents on rings C and D. These compounds can beprepared by simple hydrolysis of the carbalkoxyalkyl or carbalkoxylsubstituents and reesterification of the resulting carboxyl groups inthe C and D rings of the benzoporphyrins, or can be obtained directly bytransesterification.

It will be noted that compounds 1 and 2 and their 1,4-diene isomers areindividual species of the genus, described in the above-referenced U.S.patents, obtained through-a process which comprises a Diels-Alderreaction with protoporphyrin IX. Compounds 3 and 4 and their 1,4-dieneisomers are prepared in a completely analogous manner but usingprotoporphyrin III or protoporphyrin XIII as substrates for theDiels-Alder reaction. Since protoporphyrin IX is not symmetric withrespect to the A and B rings, two possible products result depending onwhether the Diels-Alder addition occurs in the A or B ring. On the otherhand, protoporphyrins III and XIII are symmetric with respect to theserings, and therefore only one product results in each case regardless ofthe site of addition.

In the compounds of the invention, R² is preferably vinyl, but may alsobe a derivative thereof. The vinyl group in ring A or B is readilyderivatized to other embodiments of R² by addition or oxidation. Theaddition or oxidation products can be further substituted if the addedsubstituents are functional as leaving groups, for example, --Br may besubstituted by --OH, --OR", --NH₂, --NHR", or --NR₂ ", etc., where R" isa hydrocarbon radical. For instance, one of the added substituents maybe hydrogen and the other halo, hydroxy, lower alkoxy, amino, or anamide, sulfhydryl or an organosulfide or an additional hydrogen. Thecompounds of the invention include various groups as R² includingsubstituents which provide additional porphyrin or porphyrin-relatedring systems.

Thus, R² may be vinyl, --CHOR', --CHO, --COOR', --CH(OR') CH₃,--CH(OR')CH₂ OR', --CH(SR') CH₃, --CH(NR')₂ CH₃, --CH(CN) CH₃,--CH(COOR')CH₃, --CH(OOCR') CH₃, --CH(NR'COR')CH₃, --CH(CONR'₂) CH₃,--CH(halo)CH₃, or --CH(halo)CH₂ (halo) wherein R' is H, or a hydrocarbonradical (1-6C) optionally substituted with a heteroatom substituent orwherein R² is an organic group of less than 12C resulting from direct orindirect derivatization of the vinyl group, or wherein R² is a groupcontaining 1-3 tetrapyrrole-type nuclei.

As used herein, the term "alkyl" refers to a saturated straight orbranched chain hydrocarbon which may, if it contains a sufficient numberof carbon atoms, be cyclic or contain a cyclic portion. Typical examplesare methyl, ethyl, t-butyl, cyclohexyl, and the like.

A "hydrocarbon radical" refers to a monovalent substituent containingonly carbon and hydrogen which may be straight or branched chain,saturated or unsaturated, aromatic or nonaromatic or both, and cyclic ornoncyclic. Thus, a hydrocarbon radical of 1-10C could includecyclopentylethyl, 2-pentenyl, 3-butynyl, 2,4-dimethylhexyl, and thelike.

In some embodiments of the invention, the hydrocarbon radical may besubstituted with a heteroatom-containing substituent. Such substituentsinclude --OR, --NR₂, --SR, --COOR, --CONR₂, --OOCR, --NRCOR, --SOR,--SO₂ R, --SO₃ R, halo, --CN, and the like, wherein R is H or alkyl(1-6C). Cyclic amines include pyridyl, pyrimidyl, thiazolyl, quinolyl,and so forth. Thus, they may include single ring or fused ring systemsand may contain additional heteroatoms.

It will be noted that the compounds of the invention contain at leastone chiral center and thus may exist in various stereoisomeric forms. Ifdesired, such stereoisomers, including enantiomers, may be separatedusing techniques standard in the art; however, racemic mixtures ormixtures containing more than one diastereomer may also be used. Thecompounds as indicated in formulas 1-4 and in FIG. 14, therefore, arerepresentative of the individual optical isomers, enantiomers ordiasteriomers as the case may be, as well as mixtures of theseindividual chiral isomers.

If desired, the compounds of the invention can be prepared in metallatedforms by treating the tetrapyrrole-type nucleus with an appropriate ionsuch as magnesium ion, zinc ion, stannous ion and the like, to obtain ametal complex. The metal ion may also be a radiolabel. Generally, themetal ion is inserted using the appropriate salts under conditionsstandard in the art. For example, zinc ion can be introduced by treatingthe compound with zinc acetate in 1:1 methylene chloride:methanol.

The compounds may also contain label, including radioisotopes,chromophores, and fluorescent labels. Radioisotope labeling is generallyuseful when the compounds are to be followed in vivo or used to labelspecific moieties. Useful cationic moieties that are radioisotopesinclude technetium, gallium and indium. In addition, radioisotopes ofheteroatoms, such as ¹³¹ I or ³² P, in the molecule itself, or inclusionof ¹⁴ C may be used to label the molecule.

As further described in the BPD-related patents set forth above, thecompounds of the invention may be coupled, if desired, to a targetingagent which will direct the molecule to a specific tissue or organ. Suchtargeting agents include antibodies, receptors, receptor-ligands and thelike. Linkage of the targeting agent to the compound is conducted usingstandard techniques. By a "conjugated form" is meant a compound offormulas 1-4 coupled to a targeting agent, as above described.

Preferred embodiments of the compounds of formulas 1-4 and their1,4-diene isomers include those wherein both n equal 2, or those whereinboth R¹ are ethyl or methyl, preferably methyl, and those wherein R² isvinyl. Particularly preferred are compounds of the formula ##STR4##

Both A-EA6 and B-EA6 are effective photosensitizers; it appears thatA-EA6 is the easier to formulate.

The various forms of the compounds of the invention can be used in thephotodynamic therapy techniques generally known in the art. As set forthin the Background section above, photodynamic therapy can be conductedusing a plethora of protocols and for a variety of indications. Inaddition, compounds of this type exhibit pharmacological activity in theabsence of light in some instances. Standard pharmaceuticalcompositions, including liposomal compositions as preferred, are used asdesired in such applications.

The following examples are intended to illustrate but not to limit theinvention. While the Examples illustrate and demonstrate the surprisingpharmacokinetic properties of two members of the species of theinvention, A-EA6 and B-EA6, it is expected that the remaining compoundsdescribed by formulas 1-4 and their 1,4-diene isomers will have similarvariations in these properties. Hence, the small class of compoundscontained in the present invention offers valuable additions to therepertoire of photodynamic agents useful in treating the variousconditions to which this therapy has been directed.

EXAMPLE 1 Preparation of Two Forms of EA6

A. To prepare B-EA6, the starting material is BPD-DB as the dimethylester--i.e., BPD-DB as shown in FIG. 1 wherein R¹ and R² are both COOMean R" is vinyl.

To 2.0 g (2.7 mM) BPD-DB in 50 mL ethylene glycol and 100 mLdichloromethane was added 1.0 mL sulfiuric acid. The reaction wasstirred for 18 hr. at room temperature. Then the reaction was added to astirring mixture of 100 mL 5% aqueous ammonium acetate and 100 mLdichloromethane. The organic layer was isolated and then washed twicewith 50 mL water. The solvent was removed by rotary evaporation. Thedark green residue was then chromatographed on 75 g alumina (deactivatedwith 5% water) and eluted with a gradient of 0.5%-5.0% methanol indichloromethane. The solvent from the fractions containing product wasthen removed by rotary evaporation. The residue was dried in vacuoovernight to provide 2.02 g (89%) of the analytically pure green soldtitle compound.

B. In a manner similar to that set forth in paragraph A, butsubstituting BPD-DA for BPD-DB, the isomeric form, A-EA6 was prepared.

EXAMPLE 2 Comparison of Uptake and Release of B-EA6 and BPD-MA by L1210Cells

BPD-MA or B-EA6 were incubated at 3μg/ml in the presence of 10% fetalbovine serum with 10⁷ /mL of L1210 cells, a murine leukemia cell line.Intracellular content of the photosensitizers was measured byfluorescence of cell lysates at various times. The maximum concentrationreached was 145.9 ng/10⁶ cells for B-EA6 and 149.5 ng/10⁶ cells forBPD-MA. The time course of uptake is shown in FIG. 2 as a percentage ofcell content at 60 min by which time uptake had reached a maximum inboth cases. As shown, B-EA6 is taken up more rapidly and reaches 80% ofits maximum concentration after only 5 min and reached its maximumuptake within 15 min.

The kinetics of release of these drugs from L1210 cells was measured bypreloading the cells at 3μg/ml for 1 hr and then placing the cells indrug-free medium containing 10% fetal bovine serum. Remainingintracellular drug content was measured at various time points by lysingthe cells and measuring fluorescence. As shown in FIG. 3 (again as apercent of starting intracellular content), BPD-MA and B-EA6 showeddifferent kinetics of release. Initial release of B-EA6 was much morerapid, but release was more complete in the case of BPD-MA.

It was unexpected that the in vitro pharmacokinetics of B-EA6 were morerapid than those of BPD-MA. While the higher retention of B-EA6 could beattributed to its increased size as compared to BPD-MA, the fastertransfer through the cellular membrane was unexpected.

EXAMPLE 3 Comparison of In Vivo Pharmacokinetics

Either BPD-MA or B-EA6 was administered by intravenous injection intoDBA/2 mice at a dose of 4 mg/kg using 3 mice per time point. The drugcontent of plasma, skin, liver and kidney was determined by fluorescencein the tissue extracts. FIG. 4 shows the results plotted as a percentageof the concentration in the relevant tissue 15 min postinjection. Asseen in FIG. 4, neither BPD-MA nor B-EA6 accumulated in plasma, liver orkidney; however, BPD-MA accumulated in skin within the first 3 hr; B-EA6does not.

The more rapid accumulation of B-EA6 as compared to BPD-MA, as hereconfirmed in vivo by more rapid clearance from all tissues, constitutesan advantage. The treatment with light can be carried out soon afterinjection of the photosensitizer and due to the rapid clearance, noprolonged skin or eye photosensitivity will be exhibited. Thus, thesubjects treated can resume normal lives without special precautionssuch as avoiding bright light and wearing dark eyeglasses.

The half-life of B-EA6 and BPD-MA in various tissues was then computedin the time-frame min-3 hr and the results are shown in Table 1:

                  TABLE 1                                                         ______________________________________                                        Tissue Half-Lives of B-EA6 and BPD-MA                                                     T1/2* (15 min-3 hours)                                            Tissue        B-EA6    BPD-MA                                                 ______________________________________                                        Liver         0.6       2.4                                                   Spleen        0.8      10.9                                                   Kidney        0.8       5.6                                                   Skin          1.9       0**                                                   Muscle        11.1     ND†                                             Plasma        0.6       2.0                                                   ______________________________________                                         *shown in hours                                                               **BPDMA concentration in the skin increased for up to 3 hr                    †ND = not determined                                              

The half-life of BPD-MA in this time-frame could not be computed in skinsince its concentration increased during the 3 hr period. As shown inTable 1, generally, B-EA6 has a much shorter half-life than BPD-MA inmost tissues. The lack of accumulation of B-EA6 in normal skin ascompared to BPD-MA was unexpected, and indicates more rapid clearancethan that of BPD-MA. As set forth above, this is advantageous as skinphotosensitivity is the only recognized side effect of photodynamictherapy utilizing photosensitizers.

The pharmacokinetics were also determined using an in vivo mouse tumormodel. Groups of 10 DBA/2 mice containing M1 rhabdomyosarcoma tumorswere injected intravenously with a liposomal formulation of BPD-MA atvarious dosages of 0.75-1.5 mg/kg. The tumors were irradiated with 690nm laser light at 50 or 150 J/cm² at various times after injection. Theresults, as shown in Table 2, were determined in terms of the percentageof mice in each group that were tumor-free on day 7 after injection.

                  TABLE 2                                                         ______________________________________                                        Results of Bioassay                                                           PDT Conditions                                                                Drug**  Time    Light***                                                      Dose    post IV dose      Percent Tumor Free on Day 7*                        (mg/kg) (min)   (J/cm.sup.2)                                                                            BPD-MA   B-EA6                                      ______________________________________                                        0.75    15      50        (4/5)    50%                                                30      50         70%      0%                                        1.0     15      50        100%     90%                                                30      50         90%      0%                                        1.5     180     150        70%      0%                                        ______________________________________                                         *tumor model = MI tumor in DBA/2 mice  each PDT condition was tested in 1     animals                                                                       **the drugs were liposomally formulated and injected intravenously            ***690 nm laser light.                                                   

As shown in Table 2, BPD-MA treated mice showed substantial survivalrates when postinjection times ranged from 15-180 min. On the otherhand, B-EA6 treated mice showed no response at 30 min or 180 min;however, significant responses were obtained when irradiation wassupplied after only 15 min.

These data demonstrate that PDT using B-EA6 will be effective in earlytreatment with light. The lack of effect of later times postinjectionindicates, again, rapid clearance of B-EA6 which is advantageous for thereasons set forth above.

EXAMPLE 4 Determination of LD₅₀ With and Without Serum

Either B-EA6 or BPD-MA was incubated for 1 hr with L1210 cells at arange of concentrations and exposed to 9 J/cm² broad spectrum light.This determination was made in the absence of serum and in the presenceof 10% serum. The results are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        LD.sub.50 Values                                                                          No serum                                                                             10% serum                                                  ______________________________________                                        BPD-MA        3.7 ng/ml                                                                              54.0 ng/ml                                             B-EA6         4.7 ng/ml                                                                              19.7 ng/ml                                             ______________________________________                                    

As shown, BPD-MA and B-EA6 have comparable LD₅₀ values in the absence ofserum; however, in the presence of serum, B-EA6 shows a substantiallybetter retention of effectiveness.

In most instances, the presence of serum greatly reduces thephotoactivity of agents used in PDT, such as BPD-MA. Surprisingly, B-EA6shows more affinity for cell membranes than for plasma components and isthus very slightly affected by the presence of serum in the cellularenvironment. Thus, in vivo, its activity may be higher than that ofBPD-MA and other compounds of this family.

EXAMPLE 5 In Vitro Efficacy of B-EA6

The ability of B-EA6 to exert a cytotoxic effect on L1210 cells in vitrowas further tested by incubating the cells with B-EA6 at variousconcentrations for 1 hr in the absence of serum. After excess drug wasremoved, the cells were exposed to 9 J/cm² broad spectrum light (380-750nm) and cell survival was determined by the MTT assay (Mosmann, T. etal. J Immunol Meth (1983) 65:55-63). The percentage of killed cells wascalculated in reference to survival of cells exposed to light only. At aconcentration of approximately 7 ng/ml, 80% of the cells were killed; at15 ng/ml, almost 100% of the cells did not survive. As stated above, theLD₅₀ for B-EA6 is approximately 4.7 ng/ml.

The somewhat lower effect of B-EA6 as compared to BPD-MA in vitro makeseven more unexpected the comparatively higher activity of B-EA6 ascompared to BPD-MA in vivo in the presence of serum as demonstrated inExample 4.

EXAMPLE 6 Selectivity of B-EA6 for Tumor Cells

The ability of L1210 cells to accumulate B-EA6 was compared to theability of splenocytes to do so. B-EA6 at 3 μg/ml was incubated witheach cell type and the cell content of B-EA6 was determined byfluorescence in cell lysates. FIG. 5 shows a comparison of uptake forthe two cell types in ng/10⁶ cells. As shown, L1210 cells were able totake up approximately 140 ng/10⁶ cells reaching this value afterapproximately 20 min. Spienocytes, on the other hand, accumulated lessthan 20 ng/10⁶ cells after an hour of incubation.

DBA/2 mice bearing M1 (rhabdomyosarcoma) tumor, grown subcutaneously intheir flanks, were used as a model to show that B-EA6 demonstratedselectivity for tumors. Mice were administered 0.75 mg/kg of B-EA6 in aliposomal formulation intravenously. After 15 min, a 1 cm area whichincluded a 5 mm diameter tumor was exposed to 50 J/cm² of 70 mW light of690 nm wavelength from an argon-pumped dye laser. The exposureeffectively eliminated the tumor, but did not affect the surroundingnormal skin. Thus, B-EA6 demonstrates tumor specificity.

EXAMPLE 7 Immunomodulation by B-EA6

Balb/C mice (5-8 mice per group) were tested using the delayed skinphotosensitivity assay also called the contact hypersensitivity (CHS)assay. The mice were painted in the flank with the sensitizing agentdinitrofluorobenzene (DNFB) and 5 days later, one ear is challenged withDNFB, while the other serves as a control. The swelling is an indicatorof immune response. Mice were injected intravenously with 1 mg/kgliposomal B-EA6 and either irradiated with 15 J/cm² light over the wholebody or exposed to ambient light. The ability of this treatment toprevent the immune response as demonstrated by inhibition of earswelling was determined. The results showed that administering B-EA6combined with either after irradiation with 15 J/cm² whole body light orwith ambient light decreased swelling in the test ear as compared tountreated mice. The swelling in both cases was only approximately 60% ofthe that shown in mice without treatment.

In an additional assay to determine immunomodulation, murine peritonealmacrophages were isolated, purified and activated by recombinantinterferon-γ (100 U/ml). The activated cells were incubated for 1 hr at37° C. with B-EA6 at a range of concentrations and then exposed to 690nm LED light at 5 J/cm². Expression levels of MHC I, MHC II, CD54, CD80and CD86 were determined 24 hr later using FITC conjugated antibodiesand a cell sorter. The results are shown in Table 4 for B-EA6 at 0.5ng/ml in comparison to similar experiments using BPD-MA at 2.5 ng/ml.

                  TABLE 4                                                         ______________________________________                                        Effect of Low-Dose PDT with B-EA6 on Expression Levels of                     Cell Surface Antigens by Murine Peritoneal Macrophages                                  MHC      MHC     CD54    CD80  CD86                                 Compound  Class I  Class II                                                                              (ICAM-1)                                                                              (B7-1)                                                                              (B7-2)                               ______________________________________                                        BPD-MA     99.1 ±                                                                             79.3 ±                                                                             105.4 ±                                                                             93.5%                                                                              99.2%                                (2.5 ng/ml)                                                                              4.3%    10.1%    3.0%                                              BPD-B-EA6 100.4%   71.8%   106.9%  102.3%                                                                              92.2%                                (0.5 ng/ml)                                                                   ______________________________________                                    

The results in the table are given as a percent of expression ascompared to cells treated with light only. As shown, BPD-MA and B-EA6were both able to reduce expression of MHC II, but not the remainingsurface markers. Thus, although B-EA6 has advantageous pharmacokinetics,it retains the immunomodulatory activity of BPD-MA and other compoundsof this group.

EXAMPLE 8 Effect of B-EA6 in an Arthritis Model

MRL-Ipr mice spontaneously develop arthritis; this was enhanced byintradermal injection of Freund's Adjuvant. Various numbers of MRL-Iprmice were treated with PDT on days 0, 10, and 20 after injection of theadjuvant. PDT consisted of 0.5 mg/kg liposomal B-EA6 injectedintravenously followed by exposure of the ventral part of the mice tored (560-900 nm) light at 80 J/cm² at 1 hr post-B-EA6 injection. Themice were observed and symptoms scored every 5 days for 30 days. Theresults are shown in FIG. 6 in comparison to mice similarly treated withBPD-MA and BPD-MB. As shown in FIG. 6, whether measured by the incidenceof clinical symptoms (i.e., the percentage of mice exhibiting thesesymptoms) or by the change in bimaleolar ankle width in millimeters,B-EA6 (shown as solid circles) was effective in preventing the sequellaeof adjuvant injection.

Again, the retention of immunomodulatory activity of B-EA6 isdemonstrated.

EXAMPLE 9 Effect of B-EA6 on Microvasculature

The mouse cremaster muscle model was used. B-EA6 was administeredintravenously at 2 mg/kg and starting at 5 and 15 min postinjection,surgically exposed arterioles and venules were iaradiated with light atan intensity of 25 J/cm² per 5 min beginning at 5 min and 15 min afterinjection of the B-EA6. The vessels were measured as red blood columndiameter as a percentage of controls.

The results are shown in FIG. 7. While transient vessel closure could beobtained when irradiation was started at 5 min, permanent closure wasobtained when radiation was started after 15 min.

The enhanced capacity of B-EA6 to constrict or occlude vasculature, asdemonstrated in this Example, in combination with more rapidpharmacokinetics, make B-EA6 particularly advantageous in treatingneovascular diseases in the eye.

EXAMPLE 10 Absorption Spectrum of B-EA6

BPD-MA and B-EA6 have similar absorption spectra in plasma before andafter 4-hr exposure to fluorescent (380-750 nm) light. A comparison ofthese spectra is shown in FIG. 8. The similarity of the spectrum ofB-EA6 to the spectrum of BPD-MA is advantageous since the use of BPD-MAas a therapeutic agent useful in PDT is well developed. The similarityin their spectra indicates that the same light sources can be used forB-EA6 as are successful in treatment with BPD-MA.

EXAMPLE 11 In Vitro Cytotoxicity of A-EA6

In a manner similar to that set forth in Example 5, the cytotoxicity ofA-EA6 in vitro on two different cell lines was tested and compared withBPD-MA. Either L1210 cells or the dendritic cell line D2SC/1 wasincubated for one hour at 37° C. with either A-EA6 or BPD-MA. Afterremoval of excess drug, the cells were exposed to 690 nm light at 5J/cm² light. Cell survival was determined 18-24 hours later using theMTT colorimetric assay described in Example 5. Percent cells killed wascalculated by reference to cells exposed to light only. As shown in FIG.9A, A-EA6 showed comparable cytotoxicity to BPD-MA with respect to L1210cells in the absence of serum but was markedly more toxic in thepresence of serum than BPD-MA. The open circles represent A-EA6 plusserum; the closed circles represent BPD-MA plus serum; open squaresrepresent A-EA6 in the absence of serum; and closed squares representBPD-MA in the absence of serum.

As shown in FIG. 9B, in dendritic cells where BPD-MA has an LD₅₀ of 6ng/ml and A-EA6 has an LD₅₀ of 2.7 ng/ml, A-EA6 was toxic at lowerconcentrations than BPD-MA in the presence of 5% fetal calf serum. InFIG. 9B, closed circles represent BPD-MA and open squares representA-EA6.

In a similar determination, but measuring MHC I receptors rather thancytotoxicity, A-EA6 was effective in decreasing expression of thesereceptors at lower concentrations. In this determination, dendriticcells were incubated for 1 hour at a drug concentration less than itsLD₅₀ ; 2.5 ng/ml and 5 ng/ml for BPD-MA and 1 ng/ml and 2.5 ng/ml forA-EA6. The cells were treated with 690 nm light at 5 J/cm² and thenlabeled with the appropriate antibody 3 hours post-treatment andassessed by flow cytometry. The results were measured as the percent ofthe mean channel fluorescence intensity for light-treated control cells.These results are shown in FIG. 10; BPD-MA gave an 18% and a 29%reduction, respectively, at 2.5 ng/ml and 5 ng/ml; A-EA6 lowered thechannel fluorescence by approximately 25% at both 1 ng/ml and 2.5 ng/mlconcentrations.

EXAMPLE 12 Effect of A-EA6 on Intracellular Signaling

The conditions of the study set forth in Example 11 were repeated usingHL-60 cells as the target and comparing the effects of A-EA6 and BPD-MAon cytotoxicity, on the mitogenic pathway kinase p70 S6K, and on thestress pathway kinases c-jun and HSP27. The results are shown in FIG.11. At sublethal concentrations, A-EA6 showed stronger activation of thestress pathway kinases and stronger inhibition of the mitogenic pathwaykinases.

The effect on caspase activation in HL-60 cells was also measured. A-EA6showed a stronger activation of caspases than did BPD-MA. This effect isdesirable as it is associated with apoptosis. Using apoptosis to removeunwanted cells causes the least effect on surrounding normal cells andtissues. The comparison of A-EA6 with BPD-MA is shown in FIG. 12.

FIG. 13 shows a similar comparison when percent DNA fragmentation wasmeasured in HL-60 cells. Again, A-EA6 was effective at lowerconcentrations than BPD-MA.

EXAMPLE 13 In Vivo Photodynamic Therapy Using A-EA6

In a protocol similar to that set forth in Example 3, either A-EA6 orBPD-MA was injected intravenously into mice harboring M1 tumors at adose of 1 mg/kg. This was followed by whole body irradiation with 50J/cm² of 690 nm laser light at various times after administration of thedrug. The number of tumor-free animals on day 7 was determined and theresults are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                        Photosensitizer                                                                         Irradiation time (post i.v.)                                                                  Day 7 tumor-free animals                            ______________________________________                                        BPb-MA    15 min          10/10                                                         30 min           9/10                                               A-EA6     15 min          2/2                                                           30 min          6/6                                                 ______________________________________                                         These results show AEA6 is at least as effective as BPDMA in this assay. 

EXAMPLE 14 Immunomodulatory Activity

Flanks of control and test mice were painted with the antigen DMFB andtheir ears were challenged 5 days later by pasting with the samecompound. Test animals were treated with whole-body PDT using BPD-MA orA-EA6, by injecting the photosensitizer intravenously and then exposingthe animals to red LED light at 15 J/cm². The percent suppression of earswelling was calculated in comparison to controls. The results are shownin Table 6 and indicate that A-EA6 had a stronger immunomodulatoryeffect in this assay than did BPD-MA.

                  TABLE 6                                                         ______________________________________                                        Photosensitizer                                                                            Dose (mg/kg)                                                                             Percent suppression                                   ______________________________________                                        BPD-MA       1.0        49%                                                   A-EA8        1.0        68%                                                   A-EA6        0.3        59%                                                   ______________________________________                                    

What is claimed:
 1. A method for the treatment of tumors in a subject inneed thereof comprising irradiating said subject with light afteradministration of a compound of the formula ##STR5## or their 1,4-dieneisomers or the metallated and/or labeled and/or conjugated formsthereofwherein each R¹ is independently alkyl (1-6C); each n isindependently an integer of 0-6; and R² is vinyl or a derivativethereof.
 2. The method of claim 1 wherein in said compound, R² is vinyl,--CHOR', --CHO, --COOR', --CH(OR')CH₃, --CH(OR')CH₂ OR', --CH(SR')CH₃,--CH(NR')₂ CH₃, --CH(CN)CH₃, --CH(COOR')CH₃, --CH(OOCR')CH₃,--CH(NR'COR')CH₃, --CH(CONR'₂)CH₃, --CH(halo)CH₃, or --CR(halo)CH₂(halo) wherein R' is H, or a hydrocarbon radical (1-6C) optionallysubstituted with a heteroatom substituent.
 3. The method of claim 1wherein in said compound, R² is an organic group of less than 12Cresulting from derivatization of a vinyl substituent.
 4. The method ofclaim 1 wherein in said compound, R² is a group containing 1-3tetrapyrrole nuclei.
 5. The method of claim 1 wherein said compound isin a metallated form.
 6. The method of claim 1 wherein said compound isin conjugated form.
 7. The method of claim 1 wherein said compound islabeled.
 8. The method of claim 1 wherein said compound does not containa metal ion.
 9. The method of claim 1 wherein in said compound, R² isvinyl.
 10. The method of claim 1 wherein in said compound, each R¹ ismethyl.
 11. The method of claim 1 wherein in said compound, both n are2.
 12. The method of claim 11 wherein in said compound, R² is vinyl andboth R¹ are methyl.
 13. The method of claim 1 wherein said compound isof formulas 1-4.
 14. The method of claim 13 wherein in said compound, R²is vinyl, --CHOR', --CHO, --COOR', --CH(OR')CH₃, --CH(OR')CH₂ OR',--CH(SR')CH₃, --CH(NR')₂ CH₃, --CH(CN)CH₃, --CH(COOR')CH₃,--CH(OOCR')CH₃, --CH(NR'COR')CH₃, --CH(CONR'₂)CH₃, --CH(halo)CH₃, or--CH(halo)CH₂ (halo) wherein R' is H, or a hydrocarbon radical (1-6C)optionally substituted with a heteroatom substituent.
 15. The method ofclaim 13 wherein in said compound, R² is an organic group of less than12C resulting from derivatization of a vinyl substituent.
 16. The methodof claim 13 wherein in said compound, R² is vinyl.
 17. The method ofclaim 13 wherein in said compound, each R¹ is methyl.
 18. The method ofclaim 13 wherein in said compound, both n are
 2. 19. The method of claim18 wherein in said compound, R² is vinyl and both R¹ are methyl.
 20. Themethod of claim 12 wherein said compound is A-EA6 or B-EA6 or themetallated and/or labeled and/or conjugated forms thereof.
 21. Themethod of claim 20 wherein said compound is in a metallated form. 22.The method of claim 20 wherein said compound is in conjugated form. 23.The method of claim 20 wherein said compound is labeled.
 24. The methodof claim 20 wherein said compound does not contain a metal ion.